Power supply for thermionic devices



Dec. 31, 1929. A. N. FENTON POWER SUPPLY FOR THERMIONIC DEVICES Filed Oct. 11, 1927 [A/VEIVTO fllmon Mfnfan,

A TTORNE r Patented Dec. 31, 1929 UNITED STATES PATENT-OFFICE,

ALMON N. FENTON, OF COLLING SWOOD, NEWJEBSEY, ASSIGNOR IO ATWATER KEN'I.

MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA POWER SUPPLY FOR THERJMIONIC DEVICES Application filed ember 11, 1327. Serial No. 225,469.

My invention relates to voltage regulation apparatus utilizable for any suitable purpose and particularly for maintaining substantially constant the voltage applied to the anode circuits of thermionic devices, particularly, three-electrode thermionic devices of the audion type, as utilized in radio receiving and transmitting apparatus, irrespective of variations of load in said anode circuits and of fluctuations of voltage'of a source of supply, particularly of alternating current which is rectified by an asymmetrical electrical conductor of the gaseous discharge type.

In accordance with my invention, with a regulator resistance particularly a tube of gaseous discharge type, there is associated a relay, particularly of the electro-magnetic type, to prevent application of the voltage of a supply source to a load circuit, particularly, the anode circuit of the tubes of a radio receiving set, upon failureor removal ofthe regulator tube in or from its proper circuit relation with respect to the source of supply; more particularly, the relay is associated with a regulator tube of the gaseous dis, charge type to permit application of no load voltage to the electrodes of the tube,insuring the ready formation of an ionized gaseous conduction path therein, whereupon the load circuit is connected to the source of supply and, still more particularly, in the event of an abnormal overload, for'example, as caused by improperly connecting the circuits of a radio receiving set to the supply conductors, to give an audible signal and in connection with other, apparatus, to limit the value of the overload current.

Further in accordance with my invention, in a regulator tube of the gaseous discharge type there is disposed a control electrode, preferably positioned between the anode and cathode of the tube, and in the form, of a helix spaced from and surrounding one electrode, particularly the anode, and connected directly to the other electrode particularly,

the cathode through a resistance of suitable magnitude, to improve the regulating characteristic of the tube, to reduce the load imformation of an ionized gaseous conduction path within-the tube at a relatively low.

voltage.- 7

My lnventlon residesin the features of structure, arran ement and combination hereinafter descri ed and claimed. I

For an illustration of some of the forms my invention may take, reference is to be had to the accompanying drawings, in which:

Fig. l isa diagram-of a circuit'arrange me'nt embodying my invention.

Fig. 2 is a modification of part of the circuit arrangement of F ig. 1. I

Fig. 3 is a regulator tube constructed in accordance with my invention.

Fig.4 is a sectional plan view of the tube voltage to several hundred volts. Opposite terminals of the secondary S are connected to the anodes A and A of a rectifier, particularly a rectifier tube of the gaseous discharge .type described and claimed in copending application, Serial No. 198,181, filed June 11, 1927, and the cathodes C and (3 thereof, which are electrically connected together, connect to a typical filter system comprisingthe inductance L and condensers K, K as well understood in the art for min-' imizing the hum-producing ripple. The cathodes C and C are adapted to be connected through a switch 1 to the anode or plate a of athree-electrode thermionic tube or audion V whose cathode or filament f heated bya suitable sourceof current, as a battery. B, connects with a substantially middle tap of the secondary S. The filament or negative side of the system is preferably grounded as indicated'at E. Z represents the impedance in the plate. circuit of the tube V which usually has a control grid 9. The

impedance Z may be of any suitable character depending upon the purpose and function of the tube V which may be used as a radio or audio frequency amplifier, detector, oscillation generator, etc. And it will .be under-- stood that from the same source of current the anode circuits of one or more tubes such.

as V, performing the same or difierent functions, for example, the anode circuits of one or more radio frequency amplifier tubes, a detector, and one or more audio frequency amplifier tubes as utilized in a radio receiving set, may be simultaneously supplied.

To the positive conductor of the rectifier system extending between the cathodes G, C and the switch 1, is connected an electrode 6 of a regulator tube R, of the gaseous, discharge type, the other electrode 6 of which is connected through a relay coil 2 to the negative conductor of the rectifier system. In the modification shown in Fig. 2 the anode a of a regulator tube R of the hot cathode type having the filament f, or its equivalent,

heated by current from a battery, B, or other I source of current, is connected to the positive conductor of the rectifier system and the hot cathode or filament f is connected through a relay coil 2 to the negative side of the system. In either modification the relay coil 2 may be connected between the cathode of the rectifier tube and the negative conductor of the rectifier system as-in Fig. 1 or be tween the anode of the rectifier tube and the positive conductor of the system as in Fig. 2.

In each of the above systems the switch 1, which controls the application of voltage to the load Z, is biased to the open circuit position in any suitable manner as by a spring 3 and is held in the closed circuit position by energization of the relay coil 2 or its equivalent by the current which passesbetween the electrodes of the regulator tube. Upon failure of the conductive discharge path between the electrodes, as by disintegration of electrodes or by failure of the supply circuit of the filament f of the hot cathode type regulator tube, 'or upon removal of the regulator tube from its proper circuit relation with respect to the source of current, the relay coil 2 is de-ener ize'd, permitting the switch 1 to move to its iased, open circuit position and thereby preventing the application ofunregulated and dangerously high voltage to the conductors extending to the anode A and cathode F of the thermionic device V.

It will be understood that the switch 1 may be in the negative conductor from the source of supply instead of as shown, or may have two contact blades disposed to .connect and disconnect both the positive and negative wires from the load circuit. It is desirable that the ositive or high potential connection be bro en. v 7

Referring to Fig. 1, upon closing of the switch 4, either manually or as hereinafter f described, to complete the primary circuit of the transformers PS, as no current at first flows through the relay coil 2, the switch 1 remains open and the full, no-load voltage of the rectifier system is applied directly to the electrodes, e, e of the regulator tube R which insures prompt formation of a conductive path within the tube, whereupon current flows through the relay coil 2 moving the switch 1 to the circuit closing position to con-. nect the load of the anode circuits of one or more tubes V to the source of rectified current. In the event that an abnormally heavy current is drawn from the source, as by a short circuit in or improper connection to a radio receiving set or equivalent device adapted to be connected to the source of supply, the voltage between-the electrodes 0 and 6 drops to such an extent that the conductive path between the electrodes is broken, whereupon the relay coil 2 no longer being energized is unable to maintain the switch 1 in closed circuit position against the action of spring 3, thereby disconnecting the source of short circuit or overload from the source of supply. Immediately, however, the voltage on the regulator tube electrodes resumes its original value, the conductive path is reestablished and the switch 1 again closed. This action is repeated with more or less rapidity during the continuance of the ab- ;normal condition, the buzzing of the switch 1 serving as an audible signal or warning of the existence of the abnormal condition. The frequent interruption of the circuit, par ticularly because of the high inductance of the filter choke L and the secondary coil S limits the maximum value of the short circuit current, protecting the several elementsof the source of supply.

Referring to Fig. 2, the conductors extending from the electrodes 7, a of regulator tube R are understood to be connected to the positive and negative conductors of'the rectifier system of Fig. 1 as at am. Upon closing of switch 4,- completing the primary circuit of the transformer PS, no current flows through the relay coil 2 unless the filament f of the regulator tube R has been heated to proper temperature for emission of electrons by current from battery B which may be as shown that utilized for heating the filament of valve V. A conductive path being established within the tube by emission of elec trons from the hot cathode f, current flows from the anode a, to the negative conductor of the rectifier system in a path including the relay coil 2, effecting circuit closing movement of switch 1 as above explained.

The relay coil 2 and switch 1 are so designed with respect to the regulator tube R that when a heavy current is drawn from the system, as occasioned by a short circuit in or improper connection to a radio receiving set,

or example, connected to the source of supply, the voltage between a and f falls to such a degree that the current flowing through the regulator tube is less than suiticient to energize coil 2 to a degree sufiiciently great to overcome the action of spring 3 upon switch 1 whereupon the switch opensbreaking the connection to the overloaded circuit. Immediately the load .is removed as in the system of Fig. 1, the supply voltage resumes its normal value, the current through the regulator tube and the relay coil 2 in series therewith, rises, reclosing switch 1. This action is repeated more or less rapidly during continuance of the overload, the buzzing of switch 1 serving as an indication of its existonce. The frequent interruption of the circuit because of the inductive character of elements of the rectifier system limits the maximum value of short circuit current.

It will be understood that in the event a source of direct current of suitable value is available the transformer PS and the rectiiier may be dispensed with and the terminals of the supply connected directly or through a resistance of suitable value to the conductors connected to theelectrodes of the regulator tube with the positive conductor of the source of supply connected to the anode of the tube and the negative conductor to the cathode of the tube as above described.

Referring to Fig. 3, 5 is the base of the bulb B of the regulator tube R, of glass or the like, having the usual tubular stem 6 and press 7, of glass or equivalent. Secured to or sealed in the press 7 are the upstanding supports 8, in the form of rod or wire to which are secured, as by welding, the turns of a helix which constitutes the cathode 0 the support being essential or at least desirable because of the fineness of the wire constituting the cathode. The cathode may be of tanta-v lum, tungsten, molybdenum, nickel, or other suitable material, but preferably tantalum wire ranging in diameter from about .003 to .025 inch, but preferably about .01 inch. Wire of this'fineness is of itself not sufficiently stiff or rigid to hold its form under conditions obtaining in the manuaf'cture, shipment, and particularly in the use of the valve. The cathode may be in the form of a hollow cylinder (or plate) in which event the wires 8 merely serve properly to position the electrode within the tube.

Disposed substantially in the axis of the cathode e is the -associated anode e in" the form of a rod or wire of any suitable material, such as that of the cathode 6 The diameter of the anode wire or rod ismaterially greater than that of the cathode, rendering the anode sufliciently rigid to be self-supporting and non-deforming. For example, the diameter of the anode wire may be of the order of .02

though considerablevariation in either direce tionfrom that magnitude is permissible.

Disposed within and concentric with the a cathode e is a foraminous control electrode 0 preferably in the form of a helix of fine wire whose convolutions are more closely spaced than those of the cathode e. The control elec trode may be of tantalum, tungsten, molybdenum or other suitable material butpreferably molybdenum and of Wire of the order of .005" diameter, eifecting small radius of curvature of'its surface for effecting high secondary electron emission which may be further increased by a coating of an oxide'of a rare earth metal, as mixtures of barium and strontium oxides, by decreasing the diameterof the Wire, or by both expedients. The control electrode may be a'helix of thin ribbon or a series of thin washers spaced longitudinally along a common axis. The control electrode may also be in the form ofv an open-ended cylinder, having perforations punched therethrough as shown in Fig. 5,.or a'cylinder composed of a strip of wire gauze, as shown in Fig. 6.

To preserve the proper space relation between them, the convolutions of the control electrode helix 0 are each welded to a relative w ly stiff rod or wire 9, which in turn is welded to a supporting rod or Wire 10 secured in the press 7 of the tube.

The anode may extend to any suitable distance into or longitudinally of the associated cathode and control electrode and may extend to the upper end thereof, though, as indicated, it is preferred that the anode shall terminate short of the upper end of the cathode and that the control electrode shall extend beyond both ends of the cathode.

Adjacent its emergence from the press or seal 7 the anode is surrounded by a tube 11 of refractory insulating material having a coeflicient of thermal expansion substantially equal to or difler ing but slightly from that of the glass or other material of the .press 3. The tube 11 is reasonably gas free .and at least moderately refractory and should be of a material which will effecta sufficiently close joint with the press 7 to prevent a discharge creeping along thejoint between it and the press 7 A suitable material for the tube 11 is steatite (soapstone) calcined or otherwise treated to remove water. It is understood, however, that other materials, either natural minerals or artificial compositions, as, for example, lava, lavite may be-used for the tube 11. Tube 11 is slipped over the anode and with it is fixed in positionu pon formation ofthe press into which the tube preferably extends, though it is to be understood it may terminate at the upper surface of the seal The pure gas utilized in the tube is preferably helium, though other suitable gases, such as a monato'mic gas, such as neon, argon may be employed- The absolute gas pressure is of the order of from 5 to about 50 mm. of mercury, but preferably 22 mm.

Referring to Fig. 1, the control electrode factors of tube construction as spacing of the electrodes, their size and shape, the nature of the gas content of the tube, the pressure of the gas, and particularly the electron emission of the control electrode. The resistance may be connected between the electrodes exteriorly of the tube or, as shown symbolically in Fig. 7 within the tube structure itself, as in its base.

Upon closing of the switch 4, for an instant, the control electrode 0 and the anode e are at the same potential with respect to the cathode e since no current is flowing through the resistance 12. In effect the control electrode and the anode constitute a single electrode having a relatively large area closely spaced from and at high potential with respect to the cathode c with the result that there is readily formed a conductive path between the electrodes of opposite polarity within the tube. Immediately that a current flows, there is a drop of potential in the resistance 12 and the voltage of the control electrode is intermediate that of the anode e and cathode 6 The amount of current drawn by the regulator tube R under normal operating conditions is noticeably less in this type of tube having a control electrode connected to the anode through the resistance than through the usual type of gaseous discharge regulator tube having two electrodes.

In the filament circuit of the tube V there may be provided a relay coil 13 or its equivalent whereby upon closing of the filament circuit by the filament control switch 14, the coil is energized to move the switch 4 to closed circuit position.

It is characteristic of the current supply system described that as the load is increased the voltage falls to a marked de ree and vice versa. In other words, the load voltage characteristic of the system could be graphically represented by a curve or line having an abrupt slope or a high rate of chan e. To maintain a constant voltage from such a system, the current drawn by the regulator should vary inversely and to like amount as the load upon the system varies, in order that the total load, the regulator load plus the output load in parallel, remains substantially a constant. From the standpoint of economy it is desirable that such a regulator draw a minimum current when the load cur-' rent is at its normal value. The two-electrode gaseous discharge regulator tubes heretofore used were not satisfactory from the o standpoint of regulation in that the changes of the current drawn by the regulator, although opposite in character to those of the load, were not equal or approximately equal in amount thereto. Furthermore, they imposed a considerable drain upon the current supply system when the useful load was of normal value.

In the system described as the rectified voltageincreases, due either to an increase of voltage in the source G, or to a decrease of the useful load drawn by the vacuum tube V, the internal resistance of the regulator tube R decreases, whereupon an increased current is conducted between the electrodes of the tube as in the ordinary two-electrode type. However, the current changes at a greater rate than in the two-electrode tube-and more closely approximates the value required to cause the output voltage to resume its original value. Although the total current passed by the tube is increased, the current in the branch circuit consisting of the control electrode c and the resistance 12 decreases, due to the secondary emission of electrons from thecontrol electrode 0.

Conversely, upon a decrease of the supply voltage, due either to a decrease of the voltage of the alternator G or to an increased current drawn by the tube V, the conductivity of the current path within the tube is decreased so that the total regulating current is decreased, reducing the total load on the supply system and permitting the voltage to, rise to its normal value. Similarly although the total regulating current is decreased, the current through the resistance 12 in the branch circuit increases. The efiect of the branch circuit is to produce a change in the regulating current which closely approximates or equals and is opposite in character to the change in current produced by the original voltage Variation. As -above stated, the amount of regulating current drawn by the tube R when the useful load of the tube V is at its normal value is considerably less because of the presence of the control electrode 0 and its associated resistance 12 connected to the anode e of the tube.

What I claim is I 1. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power, a voltage regulating impedance across said source and means to dis connect said source from said anode circuit having energizable means connected in series with said resistance and in shunt to said load circuit, to disconnect said source from said load circuit upon reduction of current through said impedance to less than a predetermined value.

l. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power, a regulator tube of the gaseous discharge type connected across said source, and means adapted to disconnect said source from, said anode circuit upon failure of a gaseous conductive path within said tube.

5. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power, switching mechanism adapted to connect said source of supply to said anode circuit, a voltage regulating impedance in shunt with said anode circuit, and electrical means connected in series with said regulating impedance for normally maintaining said switching mechanism in circuit closed position. v

6. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power, a relay having contact structure adapted to connect said source of supply to said anode circuit, a regulator tube of the gaseous discharge type having an electrode connected to a conductor from said source, and a coil of said relay having its terminals connected to a second electrode of said tube and to a conductor of said'source opposite in polarity to said first named conductor.

7. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power. contact structure biased to open circuit position adapted to connect said source of supply to said anode circuit, a regulator tube of the gaseous discharge type, and a coil for moving said contact structure to closed circuit position energized by current passing through said tube.

8. Apparatus for supplying power to the anode circuit of a thermionic tube comprising a source of power, switching mechanism adapted to connect said source of supply to said anode circuit, a regulator tube of the self-starting type, and means for effecting movement of said switch to closed circuit position only after said tube is in operating condition.

9. A power supply for a radio apparatus comprising a source of current, an impedance automatically to maintain constant the potential of said source, switching mechanism ada ted to connect said radio apparatus to said source of current, and means responsive to the current through said impedance repeatedlv to efl'ect opening and closing movement of said mechanism upon abnormal circuit conditions of said apparatus.

10. A power supply for radio apparatus comprising a source o fcurrent, a regulator tube for maintaining constant the potential ALMON N. FENTON.

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